| Metal-organic frameworks?MOFs?are usually formed by self-assembly of metal ions or clusters?as secondary building units,SBUs?and organic ligands.The self-assembly is closely dependent on the coordination mode of secondary building units and the length and rigidity of organic ligands under different reaction conditions,which including the type of solvent,reaction temperature,reaction time,the proportion of metal ions and organic ligands.Self-assembly of various metal ions?clusters?and organic ligands have produced a large number of MOFs materials with abundant topological structure and permanent porosity base on different synthesis methods.Owing extremely high surface area,high porosity and adjustable pore function,MOFs exhibit significant advantages over other porous materials.During the past two decades,the research topics span from gas storage,separation,catalysis,drug delivery,luminescence,to proton conduction and energy conversion.MOFs materials with desirable architecture and chemical functionality can be synthesized through judicious choice of metal ions and ligands.In this thesis,we have successfully constructed senven MOFs materials by using indium nitrate or zinc nitrate as metal source,and three kinds of tetracarboxylate ligands with low-symmetry?2,5-H4ABTC=2,2',5,5'-azobenzene tetracarboxylic acid,3,5-H4ABTC=3,3',5,5'-azobenzene tetracarboxylic acid,and H4BPTC=3,3',4,4'-biphenyl tetracarboxylic acid?as organic ligands under solvothermal conditions.According to structural analysis of these seven compounds,their properties were investigated in terms of adsorption?gas adsorption and separation,organic dyes adsorption and separation,and iodine adsorption and release?and proton conduction.The main results are focused on the following aspects:?1?MOFs 1 and 2 were synthesized by using indium nitrate and two organic ligands?2,5-H4ABTC and 3,5-H4ABTC?,which all consist of the same[In?COO?4]-secondary building units.Compound 1 has been synthesized by using2,2',5,5'-azobenzenetetracarboxylic acid?2,5-H4ABTC?as a linker,which coordinated to four[In?COO?4]-SBUs to generate a 3D framework.Compound 1 is constructed by a rare 4+4 strategy from 4-connected tetrahedral[In?COO?4]-SBUs and tetrahedral ligands,which can be described as a?4,4?-connected and forbidden interpenetrated zeolite-like MOF with GIS topology.The framework exhibits significant advantages in terms of thermal and chemical stability.The adsorption amount of CO2 for compound 1 is studied under 1 bar,which exhibits the highest CO2capture ability at 273 K among the ZMOFs materials with GIS topology.Furthermore,compound 1 shows good adsorption capacity for other small molecular gases,such as methane,ethane and propane.The adsorption properties of organic dye and iodine for compounds 1 and 2 were investigated due to anionic frameworks and pore characteristics.Compounds 1 and 2 exhibit good adsorption ability,which could efficiently adsorb small and non-anionic organic dyes.Furthermore,they also exhibit good ability for iodine sorption and release in solvents.?2?By using zinc nitrate and 2,5-H4ABTC,we have synthesized four three-dimensional MOFs 3-6 with/without second ligand.Coumpounds 3-6 are constructed by different secondary building units.Each[Zn7O2?COO?12]SBU are linked by 2,5-ABTC4-to form compound 3.By introducing 1,2,4-triazole ligand in the synthetic system,compound 4 was synthesized and it contains two types of inorganic SBUs of classical Zn-paddlewheel[Zn2?COO?4]and[Zn2?triazole?2?COO?4]clusters,which can be described as 4,6,6-connected new topology.Compounds 3 and 4 not only display excellent adsorption capacity for small molecular gases,but also exhibit good selectivity for CO2/CH4,C2H6/CH4 and C3H8/CH4.Compound 5 possesses a2-fold interpenetrated zeolite-like MOF with SOD topology based on zinc nitrate and the mixed-ligand?2,5-H4ABTC and 1H-Tetrazole?.The limiting pore size of compound 5 is just right for CO2,which could not absorb nitrogen,methane,ethane and propane.Therefore,compound 5 exhibits significant selectivity for carbon dioxide gas.By employment of the mixed-ligand strategy,2-fold interpenetrated compound 6 was successfully synthesized by the assembly of zinc nitrate,2,5-H4ABTC and 4,4'-Bipyridine ligands.?3?Compound 7 has been synthesized by using 3,3',4,4'-biphenyltetracarboxylic acid?H4BPTC?as organic ligands,which linked to[Zn?COO?4]2-secondary building units and K ions through four carboxyl groups,and generated a 3D framework.The proton-conducting properties of compound 7 were investigated by impedance spectroscopy.Compound 7 exhibits a low conductivity under anhydrous conditions,but the proton conductivity under humidified conditions significantly enhanced due to the cooperation of guest[Me2NH2]+cations,water molecules and host carboxylates.compound 7 exhibits high proton conductivity of 8.4×10-3 S cm-1 at ambient temperature?27 oC?and 98%relative humidity,it is comparable to the most reported proton-conducting MOFs materials under the same condition for powdered sample.To gain an understanding of the proton conduction mechanism,we successfully obtained a single crystal structure of 7·0.5H2O and the possible conduction pathway is proposed.The activation energy?Ea?obtained from an Arrhenius plot was 0.25 eV,indicating that the proton conduction behaviors occur through a Grotthuss mechanism. |
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